Electrostatic actuators and ultrasonic transducers may be used for various applications in a variety of media including liquids, solids, and gas. For instance, ultrasonic transducers are commonly used in medical imaging, such as for diagnostics and therapy. Other uses may include biochemical imaging, non-destructive evaluation of materials, sonar, communications, proximity sensing, gas flow measurements, in-situ process monitoring, acoustic microscopy, underwater sensing and imaging, and numerous other practical applications.
A typical CMUT may include at least two electrodes with a transducing space (e.g., a separation gap) between the two electrodes that allows one of the electrodes to be physically displaced toward and away from the other electrode during operation. On the other hand, a typical piezoelectric transducer, such as those using lead zirconate titanate (PZT) may include a ceramic disc of piezoelectric material that develops a voltage across two of its faces when compressed (such as for sensor applications), or that physically changes shape when an external electric field is applied (such as for actuator applications including ultrasonic applications).
PZT transducers may sometimes be used with an acoustic lens that is placed on the front surface of the PZT transducer to shape the acoustic beam produced by the PZT transducer. A commonly used acoustic lens material for a PZT-based ultrasonic transducer in medical imaging is RTV silicone rubber (RTV). However, the acoustic loss in RTV may be significant, especially when the PZT transducer is operated at a relatively high frequency.